Issue 1513:  Exception for creating instances of imported supertypes? (mof-rtf)
Source:  (, )
Nature:  Revision
Severity:  Minor
Summary: Summary: What exception should Reflective::RefObject::create_instance()
 raise if it is unable to create an instance of a supertype where the
 supertype is imported from another Package?
 

Resolution: resolved and closed
Revised Text: 
Actions taken:
June 9, 1998: received issue
May 8, 2000: closed issue
Discussion: 
Discussion: This issue highlights an anomaly in the mapped IDL when a Class is defined
as a subtype of an imported Class. The M1 level interfaces for the subtype Class inherit a
factory operation for the supertype Class that can't be implemented for an independent
Package instance.
Possible solutions:
1. Remove the create anomoly by forbidding generalization of imported Classes.
Problem: this is too important / useful a meta-modelling capability to lose.
2. Restructure the mapped IDL so that the anomalous operation is not inheritted. For
example, move the classes factory operation into the Package interface for the en-closing
Package. [If we move the IDL operations for classifier-level Attributes and
Operations into the Class instance interface, we can get rid to the the Class proxy
interface entirely!] Problem: this change has substantial impact on current MOF
implementations.
3. Define that the anomalous inheritted factory always returns nil or raises an excep-tion.
Problem: we don't need to go this far. In particular, if the imported Class and
the subtype Class are within the same extent, the create operation is implementable.
4. Define the behaviour of the inheritted factory operation to be valid when the Pack-age
extent includes proxies for both subtype and supertype Classes, and to raise an
exception othewise.
Proposed resolutions:
1. Add an extent-based restriction on creation of instances with an imported super-type.
Applies to instances of both the Class and its imported supertype Class.
2. Raise a new kind of structural ConstraintError when the above rule is violated.
Implementation: The supertype closure rule is defined in “The Supertype Closure
Rule” on page 5-22, and there is a new error kind "Supertype Clo-sure";
see Section 5.4.2, “Structural Errors,” on page 5-26. The
specific and reflective versions of the create operation updated to
track this. Done. [SC]
End of Annotations:=====
Return-Path: <crawley@dstc.edu.au>
To: mof-rtf@omg.org, issues@omg.org
Subject: Exception for creating instances of imported supertypes?
Date: Tue, 09 Jun 1998 16:31:30 +1000
From: Stephen Crawley <crawley@dstc.edu.au>


Source: DSTC (Dr. Stephen Crawley, crawley@dstc.edu.au)
Nature: Revision
Severity: Minor
Summary: What exception should
Reflective::RefObject::create_instance()
raise if it is unable to create an instance of a supertype where the
supertype is imported from another Package?